1. Field of the Invention
The present invention relates to an image reading apparatus that reads image recorded on a recording medium, such as a document. Furthermore, the present invention relates to an image reading apparatus and an image determining method for determining whether a read image contains a distinguishing pattern indicating a copy-protected image, such as paper money.
2. Description of Related Art
The image processing technology is well developed. The technology makes it possible optically read an image recorded on a document, such as a paper, and to form a duplication image that is a brilliant copy of the read image. For example, it is possible to make a high-quality full color copy, and to transmit a high-quality image with facsimile communication. There is an image reading apparatus that can optically read an image and make a brilliant copy of the read image, as described above. Such the image reading apparatus is often provided with a function for prohibiting to make a copy of a copy-protected image, such as a paper money or a financial security. Specifically, the image reading apparatus stores a distinguishing pattern indicating the copy-protected image and determines whether the stored distinguishing pattern is detected from the read image or not. When the stored distinguishing pattern is detected from the read image, the image reading apparatus decides that the read image is the copy-protected image, and sets to prohibit making a copy of the image.
As the image processing technology is developed greater, it increases higher the importance prohibiting to make a copy of the copy-protected image. Furthermore, as the technology is developed greater, it increases higher in number of image types whose copy should be prevented. On the other hand, a wide variety of documents is getting to be utilized with the image reading apparatus. The document may contain a pattern, as a part of the overall image, similar to the distinguishing pattern indicating the paper money, although the overall image of the document is not such the copy-protected image. In addition, the document may records an image whose colors and/or shape are similar to those of the copy-protected image. Thus, it causes higher risk that a not-distinguishing pattern is falsely detected as the distinguishing pattern and that a normal image is falsely detected as the copy-prevented image. If the detection standards are compromised in order to detect all the distinguishing patterns, it may cause higher the risk that a normal image is falsely detected as the copy-prevented image. If the detection standards are raised contrary, it may cause higher the risk that some copy-prevented images cannot be detected. Therefore, it is important to set the detection standards properly, in order to minimize the false detection and to maximize the true detection of the copy-protected image.
There is an image reading apparatus, for making a copy of read image, which is provided with one reading section for reading one surface of a document and another reading section for reading the other surface of the document. Thus, the image reading apparatus can simultaneously read an image on one surface of the document and an image on the other surface of the document. In addition, there is an image reading apparatus that has a conveyance reading mode for reading both surfaces of document passing on the conveyance path and a fix reading mode for reading both surfaces of document placed on the document table, and that can select to utilize the conveyance reading mode and the fix reading mode. It is possible to reduce the time required for reading both surfaces of the document by such the image reading apparatus that reads both surfaces simultaneously, greater than by an image reading apparatus that reverses the document after reading one surface of the document and then reads the other surface of the document. Furthermore, it is possible to simplify the conveyance path easier and reduce damage on the read document greater in the image reading apparatus that reads both surfaces simultaneously, than in the image reading apparatus that reverses the document for reading both surfaces. Moreover, it is possible to make the image reading apparatus in which a user can select the conveyance reading mode and the fix reading mode.
Generally, the image reading apparatus requires adjustment on the image reading function, in order to obtain proper results of a read image. For the adjustment, an image processing attribute of the image reading apparatus is-improved to obtain a predetermined quality of the read image. Such the image processing is known to include: shading correction for correcting the sensitivity variance of pixels or the irregular illuminance based on the light for the document in the read image; gamma correction for correcting the gray scale from bright section to dark section in the read image; color correction for correcting spectral attribute or color filter attribute of the light for the document in the color image reading apparatus and the like. The standard for the shading correction is generally obtained through reading a predetermined white board. The standards for the gamma correction and the color correction are generally obtained through reading a predetermined image. Thus, a predetermined standard image is utilized for the adjustment.
The image reading apparatus with respective reading sections for both surfaces of the document requires adjusting these two reading sections. The attribute of one reading section should be different from the characteristic of the other reading section within a permissible range, in order to prevent the difference between the image read by one reading section and the image read by the other reading section. Thus, a method is proposed for simplifying the adjustment of these two reading sections and for preventing the difference among the read images of both surfaces. For example, Japanese Patent Application Laid-Open No. 2006-42034, Japanese Patent Application Laid-Open No. 2006-135631 and Japanese Patent Application Laid-Open No. 2006-229466 propose such the method. The method in Japanese Patent Application Laid-Open No. 2006-42034 is directed for obtaining a color overlay image in which the read image of one surface of the document is overlaid on the read image of the other surface of the document. The method in Japanese Patent Application Laid-Open No. 2006-135631 is directed for simplifying the configurations of the image reading apparatus that is provided with two reading sections, reads both surfaces of the document and prevents the quality difference among the read images of both surfaces. The method in Japanese Patent Application Laid-Open No. 2006-229466 is directed for properly adjust the attributes of both reading sections and keeping the attribute of one reading section different from the attribute of the other reading section within a permissible range.